Fluid sampling can be used to effectively monitor environmental changes in water, air, or other desired fluids. For example, fluid sampling may be used to monitor water quality in ground water, lake water, and ocean water. The taking of samples may be desired over extended periods of time, on varying days, at various depths and/or in remote locations.
Many dynamic problems in hydrology, hydrogeology, and hydrogeochemistry can be addressed through detailed spatial mapping and time series measurements of the chemical and isotopic composition of water. For example, frequent and detailed water sampling may be required to understand the environmental variables that control mixing of surface and ground water, the isotopic and chemical composition of lake water, nutrient loading in estuaries and the isotopic and chemical composition of ocean water.
The need for broadly-spaced simultaneous and/or high frequency sampling, however, can result in complication and expense. Sampling can be simplified by collecting fluids of interest, for example water, using automatic samplers. Existing automatic samplers are designed predominantly for use in developed water systems, such as storm sewers and water treatment plants, which can be visited frequently. Available automatic samplers are generally not suitable for use in remote areas for several reasons. First, they do not preserve the water samples taken. For example, they generally do not prevent evaporation. This can prevent their deployment in remote areas which necessitate sampling and storage of multiple samples over an extended period of time, for example for a period of years.
In addition, many presently available automatic sampling devices are unsuitable for deployment in remote and/or deep bodies of water because they are not self contained. For example, U.S. Pat. No. 4,288,206 to Tigwell, et al. discloses a water sampler that uses multiple glass chambered syringes to collect water samples to be delivered under pressure to an external testing site, such as to a sorption column. Other such devices include components, such as a pump and sample bottles, that remain onshore. Sample collection is achieved through a tube that is extended into the water to be sampled. Accordingly, the sampling range of these devices is generally restricted to the length of the sampling hoses.
Examples of fluid samplers designed to be submersible, include U.S. Pat. No. 4,462,265 to Rein, which discloses a water sampling system for use with a ship. A mechanically powered unit equipped with a pump is lowered to a desired depth to withdraw water samples. Samples are then drawn into several collection devices placed at various depths between the unit and the ship. The pump is powered by towing movements of the ship. The invention has limited applications since it requires continuous presence at the monitoring site and is not automatic.
Other currently available samplers allow for automatic sampling, but require the use of motors and pumps to acquire the desired samples. For example, U.S. Pat. No. 5,606,138 to Saarenketo discloses a water sampling device that allows automatic sampling without the need for continuously manning the monitoring site. An electric motor and a centrifugal pump are placed in connection with a sample container to take samples of specific volumes of water at specific intervals. However, the unit resides in a buoyant container and therefore is not designed for submersion. Furthermore, the requirement of a motor and pump reduces reliability and adds additional weight and cost to the sampler.